Known in the art is a catalyst for dehydrogenation of oxygen-containing cyclohexane derivatives containing, as the active component, nickel as well as promotors--copper, chromium and sodium sulphate supported on an inert carrier (cf. U.S. Pat. No. 2,640,084 Cl. 260-621, 1953). However, this prior art catalyst possesses an insufficient productivity in dehydrogenation of mono-oxygen-containing derivatives of cyclohexane, e.g. cyclohexanol or cyclohexanone: at the temperature of 350.degree. C. the desired product--phenol--is formed at a rate of not more than 0.15 kg per 1 liter of the catalyst per hour.
Furthermore, in the dehydrogenation of cyclohexane derivatives containing more than one oxygen atom per molecule a side process of dehydration intensively proceeds in the presence of this catalyst. as a result, selectivity for the desired dihydric phenols, for example in dehydrogenation of cyclohexanediol-1,2 to pyrocatechol is very low and does not exceed 15-20%.
Also known in the art is a catalyst for dehydrogenation of oxygen-containing derivatives of the cyclohexane series which corresponds to the following general formula: ##STR2## wherein R.sub.1 is hydrogen or a C.sub.1 -C.sub.4 alkyl, R.sub.2 and R.sub.3 are radicals having the same or different meanings: --OH, --H, =O, provided that R.sub.2 and R.sub.3 are not simultaneously hydrogen, R.sub.1, R.sub.2 and R.sub.3 are attached to different carbon atoms of the cycle, into corresponding cyclic ketones and/or phenols which contains, as the active ingredient, a metal of Group VIII of the periodic system, such as nickel, as well as a promotor such as tin, and an inert carrier--silica. The atomic ratio between the metal of Group VIII and tin in this catalyst is varied within the range of from 1.7:1 to 15:1 respectively. Proportions of these components in the catalyst are selected within the following limits, percent by weight:
______________________________________ metal of Group VIII of the periodic system 2 to 20 tin 2 to 30 inert carrier the balance ______________________________________
(cf. H. E. Swift, J. E. Bozik, J. Catal., v.12, p.5/1968/; U.S. Pat. No. 3,580,970 Cl. 260-621H, 1971).
This prior art catalyst, however, has a disadvantage residing in its low productivity for ketones and phenols and an insufficient stability. Thus, in dehydrogenation of cyclohexanone the productivity (relative to phenol) of the nickel-tin catalyst of an optimal composition (atomic ratio of nickel:tin is 2.5:1) deposited on silica is 1.3 kg/1.hr at the temperature of 375.degree. C., while after 8 hours it is reduced to 1.0 kg/l.hr and even below (see FIG. 4 of the cited U.S. Patent). Similar results have been pointed to in publication by M. Masai et al. (J. Catal., v.38, p.128, 1975): upon dehydrogenation of cyclohexanone on a nickel-tin catalyst (nickel:tin=2.5:1) at the temperature of 400.degree. C. the initial productivity for phenol is 1.0 and 8 hours after only 0.6 kg/l.hr.
Selectivity of the prior art catalyst in dehydrogenation of monofunctional oxygen-containing derivatives of cyclohexane to phenol is high enough (up to 98%), though its selectivity for ketones is not high; thus, in dehydrogenation of cyclohexanol into cyclohexanone it does not exceed 50% (cf. op.cit. paper by H. E. Swist and J. E. Bozik). Especially low is selectivity of the prior art catalyst in dehydrogenation of polyfunctional oxygen-containing derivatives of the cyclohexane series into corresponding polyfunctional phenols. Thus, in dehydrogenation of cyclohexanediol-1.2 into pyrocatechol at the temperature of 330.degree. C. and below the selectivity for the desired product does not exceed 30%, whereas at 330.degree. C. side processes intensively occur, thus causing an accelerated deactivation of the catalyst.
Known is a process for dehydrogenation of oxygen-containing derivatives of the cyclohexane series of the abovegiven general formula feedstock) into corresponding cyclic ketones and/or phenols which comprises contacting oxygen-containing derivatives of the cyclohexane series with a nickel-tin catalyst of the above-mentioned composition at a temperature within the range of from 375.degree. to 400.degree. C. in the presence of hydrogen employed in the 6-fold molar excess relative to the feedstock (cf. H. E. Swift, J. E. Bozik, J. Catal., v.12, p.5/1968/; U.S. Pat. No. 3,580,970 Cl. 260-621H, 1971).
The above-discussed disadvantages of the prior art nickel-tin catalyst entail disadvantages of the process for dehydrogenation of oxygen-containing compounds of the cyclohexane series making use of this prior art catalyst. Thus, the use of a low-efficient catalyst causes a low productivity of the entire dehydrogenation process, while an insufficient stability of the catalyst results in impaired parameters of the process on the whole (the conversion of the starting materials, selectivity and yield of the desired products) with time and necessitates temporary shutdown of the dehydrogenation line for regeneration of the catalyst.
To improve stability of the catalyst, in the prior art process the catalyst composition additionally incorporates expensive platinum, chromium and sodium sulphate; this, however, substantially lowers productivity of the catalyst and the process of dehydrogenation to about 0.2 kg/l.hr.